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United States Patent |
5,620,508
|
Yamano
,   et al.
|
April 15, 1997
|
Heat meltable solid ink
Abstract
A solvent-free heat meltable solid ink is provided which ensures printed
images of good fastness without any deterioration of its coating
properties and which comprises a rosin-type resin in an amount of not less
than 10% by weight based on the total amount of the ink, and a coloring
agent comprising carbon black and an oil-soluble dye. In one embodiment of
the present invention, the oil-soluble dye is a metal complex dye.
Inventors:
|
Yamano; Tadamichi (Osaka, JP);
Arimura; Takao (Osaka, JP)
|
Assignee:
|
Fujicopian Co., Ltd. (JP)
|
Appl. No.:
|
633294 |
Filed:
|
April 16, 1996 |
Foreign Application Priority Data
| Apr 17, 1995[JP] | 7-090761 |
| Nov 10, 1995[JP] | 7-292873 |
Current U.S. Class: |
524/275; 106/31.28; 106/31.29; 106/31.61; 524/487 |
Intern'l Class: |
C09D 011/08 |
Field of Search: |
106/23 A,30 R,30 A
|
References Cited
U.S. Patent Documents
4661393 | Apr., 1987 | Uchiyama et al. | 106/31.
|
5141559 | Aug., 1992 | Shinozuka et al. | 106/22.
|
Foreign Patent Documents |
80914 | Mar., 1994 | JP.
| |
Primary Examiner: Klemanski; Helene
Attorney, Agent or Firm: Fish & Neave
Claims
What is claimed is:
1. A solvent-free heat meltable solid ink comprising a rosin resin in an
mount of not less than 10% by weight based on the total amount of the ink,
and a coloring agent comprising carbon black and an oil-soluble dye.
2. The heat meltable solid ink of claim 1, wherein the oil-soluble dye is a
metal complex dye.
3. The heat meltable solid ink of claim 1, wherein the proportions of the
carbon black and the oil-soluble dye are 95% to 20% by weight and 5% to
80% by weight, respectively, based on the total amount of the carbon black
and the oil-soluble dye.
4. The heat meltable solid ink of claim 1, further comprising, as a vehicle
component, a wax and a thermoplastic resin other than the rosin resin.
5. The heat meltable solid ink of claim 4, wherein the proportions of the
coloring agent, the rosin resin, the wax and the thermoplastic resin are
5% to 25% by weight, 10% to 30% by weight, 50% to 80% by weight and 5% to
20% by weight, respectively, based on the total amount of the ink.
Description
BACKGROUND OF THE INVENTION
The present invention relates to solid inks for use in thermal transfer
recording media adapted for thermal transfer printers to be used in
computers, facsimile transmission apparatuses, word processors, bar-code
printers and the like.
Thermal transfer recording media, in general, comprise a foundation, and an
ink comprising a vehicle such as a wax or a resin and a coloring agent
which is applied onto the foundation. Inks for use in such thermal
transfer recording media are roughly divided into two types: solid inks,
and solvent-based inks prepared by dissolving or dispersing ink components
in a solvent, by their form upon application onto the foundation. The
solvent-based inks offer a high degree of freedom for material selection
and provide diversified characteristics. However, the use of a solvent
imposes additional costs including the cost of the solvent itself and the
cost for drying on the price of the solvent-based inks. Thus, the
solvent-based inks are more costly than the solid inks.
The solid inks, on the other hand, are more advantageous than the
solvent-based inks in that a solvent is not used therein. However, there
has been a limitation imposed on materials usable in the solid inks since
the upper limit of melt viscosity of the inks is restricted due to
application onto a foundation by hot melt coating and, hence, it has been
difficult to obtain solid inks exhibiting diversified characteristics. The
restriction of a melt viscosity requires, for example, the use of a wax
having a low melt viscosity as a main component for the vehicle. The solid
inks each containing a vehicle mainly composed of a wax result in printed
images suffering poor fastness compared to those resulting from the
solvent-based inks each containing a vehicle mainly composed of a resin.
Intensive study to overcome the foregoing problems essential to the solid
inks has been made by the present inventors and led to a solid ink
ensuring printed images of rather enhanced fastness which comprises carbon
black as a coloring agent, and a vehicle containing a wax as a major
component thereof and a rosin-type resin in an amount of not less than 10%
by weight based on the total amount of the ink.
This solid ink, however, has encountered a different problem that the
carbon black and the vehicle component are separated upon heat melting of
the ink, thus degrading the coating properties of the ink.
In view of the foregoing, it is an object of the present invention to
provide a heat meltable solid ink providing printed images of enhanced
fastness with no degradation of the coating properties thereof.
The foregoing and other objects of the present invention will be apparent
from the following detailed description.
SUMMARY OF THE INVENTION
In accordance with the present invention, there is provided a solvent-free
heat meltable solid ink comprising a rosin-type resin in an amount of not
less than 10% by weight based on the total amount of the ink, and a
coloring agent comprising carbon black and an oil-soluble dye.
In accordance with an embodiment of the present invention, the heat
meltable solid ink is further characterized in that the oil-soluble dye is
a metal complex dye.
In accordance with another embodiment of the present invention, the heat
meltable solid ink is further characterized in that the proportions of the
carbon black and the oil-soluble dye are 95% to 20% by weight and 5% to
80% by weight, respectively, based on the total amount of the carbon black
and the oil-soluble dye.
In accordance with still another embodiment of the present invention, the
heat meltable solid ink is further characterized in that the ink further
comprises, as a vehicle component, a wax and/or a thermoplastic resin
other than the rosin-type resin.
In accordance with further embodiment of the present invention, the heat
meltable solid ink is further characterized in that the proportions of the
coloring agent, the rosin-type resin, the wax and the thermoplastic resin
are 5% to 25% by weight, 10% to 30% by weight, 50% to 80% by weight and 5%
to 20% by weight, respectively, based on the total amount of the ink.
DETAILED DESCRIPTION
The present invention will now be described in detail.
The present inventors have made repeated and intensive study to overcome
the problems of the heat meltable solid ink containing a rosin-type resin
as a vehicle component and reached the findings: by partially replacing
carbon black as the coloring agent with an oil-soluble dye, the
oil-soluble dye functions like a dispersant in the combination of the
carbon black and the rosin-type to ensure favorable dispersion, so that
the coloring agent and the vehicle will not be separated; and the use of a
metal complex dye, in particular, as the oil-soluble dye causes better
dispersion to occur thereby providing a smooth coating surface which in
turn prevents an image receptor from being smudged upon printing. Thus,
the present invention has been attained.
Specifically, by using a coloring agent comprising carbon black and an
oil-soluble dye in a solvent-free heat meltable solid ink containing a
rosin-type resin in an amount of not less than 10% by weight based on the
total amount of the ink, the coloring agent and the vehicle component will
not be separated upon heat melting, whereby the ink exhibits favorable
coating properties when subjected to hot melt coating. This provides a
uniform ink layer in the manufacture of thermal transfer recording media.
In addition, the use of a rosin-type resin in an amount of not less than
10% by weight based on the total amount of the ink ensures printed images
of excellent fastness.
Further, if a metal complex dye is used as the oil-soluble dye, better
dispersion will occur thereby providing an ink coat with a smooth surface
which will prevent an image-receiving paper sheet from being smudged in
printing.
In the present invention, the coloring agent comprises black and an
oil-soluble dye. The proportion of the oil-soluble dye to be used is
preferably within the range of 5% to 80% by weight, more preferably 10% to
50% by weight based on the total amount of the carbon black and the
oil-soluble dye. If the proportion of the oil-soluble dye is less than the
above range, separation of the coloring agent from the vehicle tends to be
insufficiently prevented. If the proportion exceeds the above range,
printed images having a poor density or a degraded weather resistance will
frequently result.
The proportion of the coloring agent (a mixture of carbon black and the
oil-soluble dye) to be used is preferably within the range of 5% to 25% by
weight based on the total mount of the ink. If the proportion of the
coloring agent is less than the above range, printed images having a poor
density will frequently result. If the proportion exceeds the above range,
the resulting ink is likely to exhibit an undesirably high melt viscosity,
deteriorating the coating properties.
Examples of specific oil-soluble dyes include azine dyes, monoazo dyes,
diazo dyes, metal complex type monoazo dyes, anthraquinone dyes,
phthalocyanine dyes, and triarylmethane dyes. Of these dyes, black or blue
color dyes are preferable. Such preferable dyes include Nigrosine Base,
Oil Black and Varifast Black (available from ORIENT KAGAKU KOGYO KABUSHIKI
KAISHA), Aizen Spilon Black and Aizen Spilon Blue (available from HODOGAYA
CHEMICAL CO., LTD.), Sumiplast Black (available from SUMITOMO CHEMICAL
COMPANY LIMITED), Diaresin (available from MITSUBISHI CHEMICAL
CORPORATION), and so forth. Of these, Varifast Black and Aizen Spilon
Black are metal complex dyes (premetallized dyes). The above exemplified
oil-soluble dyes may be used either alone or in combination.
The solid ink according to the present invention contains the foregoing
coloring agent and rosin-type resin as essential components. The
proportion of the rosin-type resin to be used is not less than 10% by
weight based on the total amount of the ink.
Examples of specific rosin-type resins include rosins, hydrogenated rosins,
disproportionated rosins, rosin esters, rosin-modified phenolic resins,
rosin-modified maleic acid resins, and rosin-modified xylene resins. These
may be used either alone or in combination.
In the present invention, the solid ink is incorporated with not less than
10% by weight of the rosin-type resin to enhance the fastness of resulting
printed images. If the proportion of the rosin-type resin is too great,
the transferability of the ink may be deteriorated, or the melt viscosity
of the ink may become too high to avoid a decrease in productivity and a
deterioration in the coating properties. From this viewpoint, the
proportion of the rosin-type resin is preferably not greater than 30% by
weight based on the total amount of the ink.
In the solid ink of the present invention, the vehicle component may
comprise, in addition to the rosin-type resin, a wax and/or a
thermoplastic resin other than the rosin-type resin. To ensure favorable
coating properties in hot melt coating, it is preferable that the ink is
incorporated with a wax in an amount of 50% to 80% by weight based on the
total amount of the ink.
Further, to impart a resulting ink layer with a flexibility and appropriate
film properties, the ink is preferably incorporated with a thermoplastic
resin other than the rosin-type resin in an amount of 5% to 20% by weight
based on the total amount of the ink.
Examples of specific waxes usable in the solid ink include natural waxes
such as paraffin wax, microcrystalline wax, haze wax, bees wax, carnauba
wax and candelilla wax; synthetic waxes such as polyethylene wax,
Fischer-Tropsch wax and .alpha.-olefin-maleic anhydride copolymer wax;
oxidized waxes or modified waxes of the foregoing natural waxes or
synthetic waxes; higher fatty acids such as myristic acid, palmitic acid,
stearic acid and behenic acid; and substances having a wax-like property
such as higher aliphatic alcohols and higher fatty acid esters. These
waxes may be used either alone or in combination.
Examples of specific thermoplastic resins (including elastomers) usable in
the solid ink include olefin copolymer resins such as ethylene-vinyl
acetate copolymer and ethylene-acrylic ester copolymer, polyamide resins,
polyester resins, epoxy resins, polyurethane resins, acrylic resins, vinyl
chloride resins, cellulosic resins, vinyl alcohol resins, petroleum
resins, phenolic resins, styrene resins, vinyl acetate resins, elastomers
such as natural rubber, styrene-butadiene rubber, isoprene rubber and
chloroprene rubber, polyisobutylene and polybutene. These thermoplastic
resins may be used either alone or in combination.
Preferable formula of the solid ink according to the present invention is
shown in Table 1.
TABLE 1
______________________________________
Ingredient % by weight
______________________________________
Coloring agent* 5-25
Rosin-type resin 10-30
Wax 50-80
Thermoplastic resin
5-20
______________________________________
*Note that the coloring agent contains 95% to 20% by weight, particularly
90% to 50% by weight of carbon black and 5% to 80% by weight, particularl
10% to 50% by weight of an oilsoluble dye.
The solid ink of the present invention may be admixed with typical
additives for use in this type of inks such as a dispersant, antistatic
agent, antioxidant and ultraviolet absorber.
The solid ink of the present invention can be prepared by uniformly
kneading the above ingredients at a temperature higher than the melting
point of the vehicle.
The solid ink of the present invention can be used in various types of
thermal transfer recording media such as one-time use type wherein a
uniform layer of a thermal transfer ink is formed on a foundation,
ink-exudation type for multiple-time use wherein a non-transferable porous
layer containing a thermal transfer ink is formed on a foundation, and
ink-shaving type for multiple-time use wherein a thermal transfer ink
layer admixed with a barrier material (particulate material such as carbon
black) is formed on a foundation so that the ink layer is gradually shaved
in the thicknesswise direction upon every heating for transfer.
Examples of foundations for use in the present invention include polyester
films such as polyethylene terephthalate film, polyethylene naphthalate
film and polyarylate film, polycarbonate films, polyamide films, aramid
films, and other various plastic films commonly used for the foundation of
ink ribbons of this type. Thin paper sheets of high density such as
condenser paper can also be used. The thickness of the foundation is
usually from about 1 to about 10 .mu.m, preferably about 2 to about 7
.mu.m, so as to ensure good heat conduction and maintain a sufficient
strength.
On the side of the foundation opposite to the side coated with the thermal
transfer ink layer may be formed a conventionally known stick-preventive
layer. Materials for forming such a stick-preventive layer include various
heat-resistant resins such as silicone resin, fluorine-containing resin
and nitrocellulose resin, and other resins modified with these
heat-resistant resins, and mixtures of the foregoing heat-resistant resins
and lubricating agents.
The present invention will be more fully described by way of examples and
comparative examples thereof. It is to be understood that the present
invention not limited to these examples, and various changes and
modifications may be made in the invention without departing from the
spirit and scope thereof.
EXAMPLES 1-6 AND COMPARATIE EXAMPLES 1-4
Solid inks were prepared by melting and kneading ingredients shown in Table
2 with a triple roll mill.
The solid inks thus prepared were each applied in a coating amount of 4.0
g/m.sup.2 onto a 6 .mu.m-thick polyethylene terephthalate film with a hot
melt coater to form a thermal transfer recording medium.
Each ink and each thermal transfer recording medium were evaluated for the
following items. The results are shown in Table 2.
In evaluating the transferability, scratch proofness and density of printed
images, each thermal transfer recording medium was used in a bar-code
printer (B-30, available from TEC Corporation) to print a bar-code image
on a high-quality paper sheet (Bekk smoothness: 140 seconds) at a printing
energy of 20 mJ/mm.sup.2.
Transferability
Bar-code images thus obtained were observed for evaluation according to the
following criterion.
.smallcircle.: any void not observed with good sharpness;
X: many voids observed with significantly degraded sharpness.
Scratch proofness
Using a crock meter (available from ATLAS ELECTRIC DEVICE COMPANY in
U.S.A.), a piece of cloth was moved back and forth 30 times on the
bar-code images under a pressure of 500 g/cm.sup.2, followed by evaluation
of the resulting smudge of the image-printed surface due to the ink
scrubbed by observation according to the following criterion.
.smallcircle.: any smudge not observed on the image-printed surface;
X: smudge observed on the image-printed surface.
Image density
The reflection optical density (OD value) of the bar-code images was
measured using a reflection densitometer (Macbeth RD-914).
Smudge preventability
Each image-receptor paper sheet subjected to printing under the above
conditions was observed for smudge of the paper sheet due to rubbing with
each thermal transfer recording medium for evaluation according to the
following criterion.
Excellent: no smudge observed;
Good: little smudge observed;
Bad: conspicuous smudge observed.
Separation of ink
Each ink in a test tube was allowed to stand in a temperature-controlled
bath at 140.degree. C. for 94 hours, and then observed and evaluated for
its separation state according to the following criterion.
.smallcircle.: No separation of ink observed;
X: Separation of ink observed.
Note that solid inks with occurrence of separation were not used to
manufacture thermal transfer recording media and hence not evaluated for
transferability, scratch proofnes, image density and smudge
preventability. This is reflected by character "--" in the rows of
evaluation in Table 2.
TABLE 2
__________________________________________________________________________
Com.
Com. Com. Com.
Ex. 1
Ex. 2
Ex. 3
Ex. 4
Ex. 5
Ex. 6 Ex. 1
Ex. 2
Ex.
Ex.
__________________________________________________________________________
4
Formula of ink (% by weight)
HNP5*.sup.1 50.0
40.0 40.0
50.0 40.0
40.0 50.0
50.0 50.0 40.0
Carnauba No. 3*.sup.2
20.0
10.0 20.0
20.0 20.0
30.0 30.0
30.0 20.0 10.0
Super Ester A-100*.sup.3
10.0
30.0 -- -- 10.0
10.0 -- -- -- 30.0
Tamanol 135*.sup.4
-- -- 20.0
10.0 10.0
-- -- -- 10.0 --
EVA*.sup.5 10.0
10.0 10.0
10.0 10.0
10.0 10.0
10.0 10.0 10.0
Carbon black 9.0
9.0 9.0
5.0 5.0
8.0 9.0
10.0 10.0 10.0
Nigrosine Base EX*.sup.6
1.0
-- 1.0
-- 5.0
-- 1.0
-- -- --
Oil Black 860*.sup.7
-- 1.0 -- 5.0 -- -- -- -- -- --
Aizen Spilon Black BH*.sup.8
-- -- -- -- -- 2.0 -- -- -- --
Evaluation
Transferability .smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
-- --
Scratch proofness
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x x -- --
Image density (OD value)
1.8
1.9 1.8
1.6 1.6
1.7 1.8
1.8 -- --
Smudge preventability
Good
Good Good
Good Good
Excellent
Good
Good -- --
Separation of ink
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
.smallcircle.
x x
__________________________________________________________________________
*.sup.1 : Paraffin wax available from NIPPON SEIRO CO., LTD.
*.sup.2 : Carnauba wax available from Toyo Ink Manufacturing Co., Ltd.
*.sup.3 : Rosin ester available from ARAKAWA KAGAKU KOGYO KABUSHIKI KAISH
*.sup.4 : Rosinmodified phenolic resin available from RIKA HERCULES CO.,
LTD.
*.sup.5 : Ethylenevinyl acetate copolymer resin (ethylene/vinyl acetate =
72:28 in weight ratio, melt flow rate: 15)
*.sup.6 : Oilsoluble dye available from ORIENT KAGAKU KOGYO KABUSHIKI
KAISHA
*.sup.7 : Oilsoluble dye available from ORIENT KAGAKU KOGYO KABUSHIKI
KAISHA
*.sup.8 : Oilsoluble dye (metal complex dye) available from HODOGAYA
CHEMICAL CO., LTD.
In addition to the materials and ingredients used in the Examples, other
materials and ingredients can be used in Examples as set forth in the
specification to obtain substantially the same results.
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